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There are definite risks that you are taking when you decide to overclock your system
processor. There is much debate over what the risks are, ranging from "don't worry,
be happy" attitudes from many hackers to those who think overclocking is very
dangerous (I guess I'm close to being in that category, although I think it is reasonable
in some circumstances). I hope to list here the dangers but with a reasonable indication
of how likely they are, and really I don't think I'm going off the deep end with any of
this stuff.

Here are the possible outcomes you can expect when you overclock your processor. These
apply to raising the clock speed of the processor only, if you are changing the system bus
speed above its nominal rating you will need to read
here as well.

Success: The processor may overclock perfectly, and run stably for many years to
come. There are thousands of people who have done this, and I am certainly not going to
deny it. This is the best case outcome.

Immediate Destruction: It is possible to totally destroy a processor by
attempting to overclock it. By destruction, I mean that the processor will not boot at the
higher speed, and when returned to its normal speed, will continue to not function. This
is basically the worst case outcome. This sort of permanent failure is very rare,
but it does happen. It is made more likely by using inadequate cooling, and also by being
ridiculously aggressive in how far you try to overclock (i.e., trying to run a Pentium 75
at 166 MHz.)

Non-Functionality: The processor may not work at the new speed, but may work fine
when returned to its original speed. This is a fairly common outcome when overclocking,
and in most cases the processor will not be any the worse for wear.

System Instability: The processor may boot at the new speed, but you may see the
system behave strangely. Random hard lockups, parity errors, resource conflicts, strange
hard disk problems, beeping, application crashes and Windows refusing to boot are just the
tip of the iceberg. Particularly insidious are the overclocks that work almost
perfectly, because that occasional crash may be due to your operating system, but it
may be due to that overclocked chip also.

Data Loss: It is very possible to lose data as a result of overclocking. If the
processor is not functioning properly, you risk potentially damaging the structures of
your hard disk's file system. It is also not uncommon for the Windows registry files to
become corrupted, requiring a complete Windows reinstall. Needless to say, a full backup
before overclocking is a wise move.

Electromigration: When the processor is run at a speed that is higher than it is
supposed to be run at, there is a chance that the internal components in the processor may
break down over time. The internal features of a CPU are sized in the range of microns. It is
possible that when the processor is stressed by running at too high a frequency, along
with the extra heat that overclocking incurs, that the actual metal lines inside the
processor may form shorts or opens and damage the processor over a period of time. How
likely this is to happen, and how long it takes is really not known. The system may work
fine for a while and then suddenly stop working.

In addition to the above, you should realize that overclocking a processor will reduce
its serviceable lifetime. How long? Nobody can really say for sure, because nobody really
knows how long a processor will last without overclocking. Controlling heat is a
big part of this equation. When you see people on the 'net saying things like
"without overclocking the chip would last 10 years and with overclocking it will last
5 years, so what do I care because I get a new chip every 2 years", just remember
that they really have no way of knowing that they are reducing the CPU's lifespan by only
50%--it could be 90%. (And I don't know about you, but even when I upgrade, I don't throw
out my old equipment if it still works...)

Also consider that hardware is not static; it ages, it changes over time--and it
degrades over time. Even if overclocking works today, it may be working because you are just
within the limits of what the system can handle. This doesn't mean that in six months or a
year, changes in the hardware due to aging, heat or other stress factors won't cause
failures or strange behavior to crop up.